1. Field of the Invention
The present invention relates to the fluorination of hydrochlorocarbons and hydrochlorofluorocarbons. More particularly, the invention pertains to the catalytic fluorination of hydrochlorocarbons and hydrochlorofluorocarbons in the liquid phase. The process is useful for fluorinating hydrochloropropanes, hydrochlorofluoropropanes, hydrochloropropenes and hydrochlorofluoropropenes and most particularly useful for fluorinating 1,1,1,3,3-pentachloropropane to 1,1,1,3,3-pentafluoropropane.
2. Description of the Prior Art
In recent years there has been universal concern that completely halogenated chlorofluorocarbons (CFCs) might be detrimental to the Earth's ozone layer. Consequently, there is a worldwide effort to use fluorine-substituted hydrocarbons which contain fewer or no chlorine substituents.
Hydrofluorocarbons (HFCs) are of great interest due to their potential to replace ozone depleting CFCs and hydrochlorofluorocarbons (HCFCs) in a variety of applications such as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. It is known in the art to produce fluorocarbons such as HFCs by reacting hydrogen fluoride with various hydrochlorocarbon compounds. In this regard, 1,1,1,3,3-pentafluoropropane (HFC-245fa), a hydrofluorocarbon having zero ozone depletion potential, is being considered as a replacement for CFCs such as dichlorodifluoromethane in refrigeration systems and trichlorofluoromethane as a blowing agent. See U.S. Pat. No. 2,942,036, Canadian 684,687, EP 381 986A, JP 02,272,086, WO 95/04022, U.S. Pat. No. 5,496,866 (foam blowing agent) and European Patent No. 2,942,036 (aerosol propellant).
Methods to produce HFC-245fa are also known in the art. See, e.g. WO 95/04022 (reaction of 3-chloro-1,1,1,3,3-pentafluoropropane with hydrogen over a reduction catalyst); WO 94/29,251 (hydrogenation of 1,1,3,3,3-pentafluoropropene with hydrogen in the gas phase at 40-300.degree. C. using a palladium catalyst; European Patent 611,744 (hydrogenation of di- or trichloropropanes); U.S. patent application Ser. Number 08/519,857, filed Aug. 25, 1995 (reaction of carbon tetrachloride with vinyl chloride to give CCl.sub.3 CH.sub.2 CHCl.sub.2 (HCC-240fa) followed by fluorination with HF in the presence of a fluorination catalyst including pentavalent antimony, niobium, arsenic and tantalum halides and mixed halides. However, these methods are not without their shortcomings. For example, hydrogenation of mono-, di- or tri-chloropentafluoropropanes and unsaturated pentafluoropropene has several disadvantages, namely, multiple steps necessary for the preparation of the feed materials, a higher reaction temperature and poor selectivity to the desired product. Fluorination of HCC-240fa with HF in the presence of a pentavalent antimony halide catalyst shows a high corrosion rate when a metallic reactor is used. See U.S. Pat. No. 4,138,355.
Also known in the art are reactions of unsaturated, halogenated olefins such as tri- and tetrachloroethenes with HF in the presence of tantalum pentafluoride, niobium pentafluoride, molybdenum pentachloride, and titanium tetrachloride. See Feiring, A. E. in Journal of Fluorine Chemistry, 14, 7(1979); U.S. Pat. No. 4,258,225 (tantalum pentafluoride and niobium pentafluoride as liquid phase catalysts).
Other known fluorination catalysts include tin salts or organotin compounds along with oxygen-containing compounds, see European Patent Application 187,643 (production of 1,1-dichloro-1-fluoroethane, HCFC-141b), tin tetrachloride, see U.S.S.R. Patent 341,788 (liquid-phase process to produce 1,1-difluoroethane, HFC-152a from vinyl chloride), and mixtures of pentavalent and trivalent antimony halides, U.S. Pat. No. 4,138,355 (production of CF.sub.3 CH.sub.2 CH.sub.2 Cl, HCFC-153fb, from 1,1,1,3-tetrachloropropane, CCl.sub.3 CH.sub.2 CH.sub.2 Cl, HCC-250fb). All of the foregoing patents and application are incorporated herein by reference.
It would be advantageous to achieve the catalytic fluorination of HCCs and HCFCs with HF under less corrosive conditions using metal reactors. The use of tetravalent tin or titanium halide or an equal molar mixture of trivalent and pentavalent antimony halides or molybdenum pentahalide as a fluorination catalyst to fluorinate polychlorinated compounds with a --CHF.sub.y Cl.sub.2-y, wherein y=0 or 1 end group to give polyfluorinated compounds with a --CHF.sub.2 terminal group is not known in the art. In particular, fluorination of HCC-240fa with HF to form HFC-245fa in the presence of tin, titanium, molybdenum or mixture of antimony(V) and antimony(III) halides is not known in the art.